Aqueous liquid formulations of pyrazoline brighteners

ABSTRACT

The claimed liquid formulations contain an organic acid and a branched mono- or di-alcohol. The addition of the alcohol improves the storage stability of the liquid formulations.

It is known to use certain pyrazoline brighteners, which bear basic groups and are present in the form of their salts with lactic acid, for brightening acrylic fibers (DE 3 134 942). A commercially available aqueous liquid formulation of such a brightener contains lactic acid, formic acid and methoxypropanol as well as the brightener. However, this formulation is still in need of improvement with regard to its stability in storage. It is thus an object of the present invention to provide aqueous liquid formulations of pyrazoline brighteners that have improved stability in storage. It has now been found that this object is achieved when a branched mono- and di-alcohol is added to the formulation of this brightener type.

The invention accordingly provides aqueous liquid formulations of pyrazoline brighteners of the formula

where

-   X is O, SO₂, SO₂NZ or a direct bond, -   Y is an alkylene chain which may be interrupted by O, S or CONH, -   Z is H or alkyl, -   R₁ and R₂ are singly an alkyl, cycloalkyl or aralkyl radical or     together the remaining members of an N-heterocycle, -   Z₁ is H or alkyl, -   Z₂ is H, alkyl or aryl, and -   A is an anion of an organic acid,     wherein these liquid formulations contain an organic acid and a     branched mono- or di-alcohol as well as a pyrazoline brightener of     the above formula.

Suitable alkyl radicals R₁ and R₃ are especially those having 1 to 4 carbon atoms, which may be substituted by halogen such as fluorine, chlorine and bromine hydroxyl groups, cyano groups, C₁-C₄-alkoxy groups, phenoxy groups, C₂-C₅-alkylcarbonyloxy groups or C₂-C₅-alkoxycarbonyloxy groups.

Suitable cycloalkyl radicals R₁ and R₂ are cyclopentyl and cyclohexyl radicals.

Suitable aralkyl radicals R₁ and R₂ are especially benzyl and phenylethyl radicals.

Suitable heterocyclic radicals which can be formed by R₁ and R₂ combining with the nitrogen atom are for example pyrrolidine, piperidine, imidazole, morpholine and thiomorpholine radicals.

Suitable alkyl radicals Z, Z₁ and Z₂ are especially unsubstituted alkyl radicals having 1 to 4 carbon atoms.

Suitable aryl radicals Z₂ are in particular phenyl radicals, which may be substituted by one or more halogen atoms, C₁-C₄-alkyl groups, C₁-C₄-alkoxy groups, cyano groups, carboxylic ester groups and carboxamide groups.

Useful alkylene radicals Y are especially those having 2 to 4 carbon atoms such as

The anion A⁽⁻⁾ may be an anion of a low molecular weight organic acid, examples being formate and lactate.

Preferred pyrazoline brighteners are those of the formula

where

-   D is —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂OCH₂CH₂,

-   R₁′ and R₂′ are each C₁-C₂-alkyl, -   T₁, T₂, T₃ are H, CH₃ or Cl and -   A is lactate or formate.

Preferably, T₁-T₃ do not represent Cl or CH₃ at one and the same time.

The amount of these pyrazoline brighteners in the ready-prepared liquid formulation can be 1% to 60% and preferably 5% to 30% by weight.

The pyrazoline bases which underlie the brightener salts defined above are known and are described for example directly or indirectly (as quaternary salts) in the following patent literature: DE-A 1 155 418, 1 237 124, 1 469 222, 1 904 424, 2 011 552, 2 050 725, 2 248 772, 2 534 180 and 2 700 996 and U.S. Pat. No. 3,131,079 and also 3 135 742. As well as the brightener salt, the liquid formulations of the invention additionally contain organic acids and branched mono- or di-alcohols. Useful organic acids include low molecular weight organic acids of the kind which are customary for salt formation of pyrazoline bases, for example formic acid, acetic acid or lactic acid or mixtures of such acids. The amount of these acids based on the ready-prepared liquid formulation is generally in the range from 20% to 60% and preferably from 30% to 50% by weight.

The fraction of branched mono- or di-alcohol in the ready-prepared liquid formulation can be 15% to 40% and preferably 20% to 30% by weight. Preferred mono- or di-alcohols are neopentylglycol and tertiary butanol.

In addition, the liquid formulations of the invention can contain the auxiliaries customary for optical brighteners, such as for example hydrotropic agents (urea for example), solution-stabilizing agents (ethylene glycol diacetate for example), preservatives, water-soluble cationic shading dyes, each in amounts of up to 10% by weight.

The liquid formulations of the invention are preferably prepared by adding the individual components of the formulation in the following order and mixing them in a suitable manner: organic acid, branched mono- or di-alcohol, brightener salt, water. Instead of the brightener salt it is also possible to start from the underlying base and to increase the amount of organic acid by the amount needed for salt formation.

The liquid formulations of the invention have an improved stability in storage compared with the hitherto customary commercial form. This improved storage stability shows itself in that the color coordinates of these formulations rise distinctly less on prolonged storage in particular.

The liquid formulations of the invention are used in a conventional manner for incorporation into spinning dopes for the production of polyacrylonitrite fibers in the so-called wet-spinning process or for brightening ready-prepared acrylic fibers in an exhaust process.

EXAMPLES

A liquid formulation was prepared by intensively mixing the following components at room temperature in this order:

40 g of lactic acid; 6 g of formic acid; 23.3 g of neopentylglycol (90% pure); 19.2 g of brightener (about 79% pure); 11.5 g of water. The brightener used has the formula

This liquid formulation was tested for storage stability (measurement of the color coordinates x and y) together with a commercially available liquid formulation of the same brightener. The commercially available liquid formulation contains 21 g of methoxypropanol and 13.8 g of water instead of 23.3 g of neopentylglycol and 11.5 g of water with the composition otherwise identical to that of the formulation of the invention.

The following x and y values were measured as a measure of stability for both formulations:

Inventive Commercial formulation material x value y value x value y value At the start 0.353 0.390 0.354 0.392 After 4 weeks' 0.362 0.404 0.368 0.401 storage RT/dark After 4 weeks' 0.363 0.402 0.402 0.425 storage 50° C./dark After 10 weeks' 0.383 0.433 0.390 0.433 storage RT/dark After 10 weeks' 0.386 0.428 0.449 0.466 storage 50° C./dark These values show that the color coordinates rise distinctly less for the formulation of the invention compared with the commercial material. This indicates superior stability for the inventive formulation, which contains neopentylglycol. 

1. An aqueous liquid formulation comprising an organic acid, a branched mono- or di-alcohol and a pyrazoline brightener of the formula

wherein X is O, SO₂, SO₂NZ or a direct bond, Y is an alkylene chain, Z is H or alkyl, R₁ and R₂ are singly an alkyl, cycloalkyl or aralkyl radical or together the remaining members of an N-heterocycle, Z₁ is H or alkyl, Z₂ is H, alkyl or aryl, and A⁽⁻⁾ is an anion of an organic acid.
 2. The aqueous liquid formulation comprising an organic acid, a branched mono- or di-alcohol, and a pyrazoline brightener compound of the formula

wherein D is —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂—OCH₂CH₂,

R₁′ and R₂′ are independently C₁-C₂-alkyl, A⁽⁻⁾ is an anion of an organic acid, and T₁, T₂, T₃ are independently H, CH₃ or Cl.
 3. The aqueous liquid formulation according to claim 1, wherein the organic acid is lactic acid, formic acid, or acetic acid or mixtures thereof.
 4. The aqueous liquid formulation according to claim 1, wherein the branched mono- or di-alcohol is neopentylglycol or tertiary butanol.
 5. The aqueous liquid formulation according to claim 1, further comprising 20% to 60% by weight of the organic acid.
 6. The aqueous liquid formulation according to claim 1, further comprising 15% to 40% by weight of the branched mono- or di-alcohol.
 7. The aqueous liquid formulation according to claim 1, further comprising 1% to 60% by weight of the pyrazoline brightener.
 8. The aqueous liquid formulation according to claim 1, further comprising at least one customary auxiliary.
 9. The aqueous liquid formulation according to claim 1, wherein Y is an alkylene chain interrupted by O, S, CONH.
 10. The aqueous liquid formulation according to claim 2, wherein D is


11. The aqueous formulation according to claim 2, wherein A⁽⁻⁾ is lactate or formate.
 12. A method for brightening an acrylic fiber comprising the step of incorporating an aqueous formulation according to claim 1 in the wet-spinning process or exhaust process for the acrylic fiber.
 13. A method for brightening an acrylic fiber comprising the step of brightening the acrylic fiber with an aqueous formulation as claimed in claim
 1. 